JP6941808B2 - All solid state battery - Google Patents

Description

The present invention relates to a positive electrode layer, a negative electrode layer, a solid electrolyte layer, and an all-solid-state battery using the same.

In recent years, there has been a demand for the development of rechargeable batteries that can be used repeatedly by reducing the weight and cordlessness of electronic devices such as personal computers and mobile phones. Secondary batteries include nickel cadmium batteries, nickel hydrogen batteries, lead storage batteries, lithium ion batteries, etc., but lithium ion batteries are attracting attention because of their features such as light weight, high voltage, and high energy density. ..

A lithium ion battery is composed of a positive electrode layer, a negative electrode layer, and an electrolyte arranged between them. The electrolyte is an electrolytic solution or a solid in which a supporting salt, for example, lithium hexafluoride, is dissolved in an organic solvent. Electrolytes are used. Currently, widely used lithium-ion batteries are flammable because an electrolytic solution containing an organic solvent is used. Therefore, materials, structures, and systems are needed to ensure safety. On the other hand, by using a nonflammable solid electrolyte as the electrolyte, it is expected that the above-mentioned materials, structures, and systems can be simplified, and it is possible to increase the energy density, reduce the manufacturing cost, and improve the productivity. It is thought that it can be done. Hereinafter, a lithium ion battery using a solid electrolyte will be referred to as an "all-solid-state battery".

Solid electrolytes can be broadly divided into organic solid electrolytes and inorganic solid electrolytes. The organic solid electrolyte has an ionic conductivity of ^{about 10-6} S / cm at 25 ° C., which is extremely lower than that of the ^{electrolytic solution of 10-3 S / cm.} Therefore, it is difficult to operate an all-solid-state battery using an organic solid electrolyte in an environment of 25 ° C. Examples of the inorganic solid electrolyte include an oxide-based solid electrolyte and a sulfide-based solid electrolyte. These ionic conductivitys are 10 ^-4 to 10 ^-3 S / cm. Oxide-based solid electrolytes have high grain boundary resistance. Sintering and thinning of powders have been studied as means for reducing grain boundary resistance, but when sintered, the constituent elements of the positive electrode or negative electrode and the constituent elements of the solid electrolyte are mutually diffused by treatment at a high temperature. Therefore, it is difficult to obtain sufficient characteristics. Therefore, the mainstream of all-solid-state batteries using oxide-based solid electrolytes is to study thin films. On the other hand, since the sulfide-based solid electrolyte has a smaller grain boundary resistance than the oxide-based solid electrolyte, good properties can be obtained only by compression molding of the powder, and therefore, research has been actively promoted in recent years. There is.

The coating type all-solid cell is a negative electrode active material formed on a positive electrode layer containing a positive electrode active material, a solid electrolyte and a binder formed on a current collector made of a metal foil, and a current collector made of a metal foil. It is composed of a negative electrode layer containing a solid electrolyte and a binder, and a solid electrolyte layer containing a solid electrolyte and a binder arranged between them. The coating type all-solid-state battery is produced by slurrying each material of the positive electrode layer, the negative electrode layer, and the solid electrolyte layer with an organic solvent and forming a film on a metal foil. When the organic solvent is dried, the coating type all-solid-state battery is produced. , It is environmentally unfavorable because a large amount of organic solvent is released.

Patent Document 1 describes a low environmental load type that does not contain an organic solvent and contains a positive electrode active material, a negative electrode active material, a solid electrolyte, and a binder, which are materials of a positive electrode layer, a negative electrode layer, and a solid electrolyte layer. A method for manufacturing an all-solid-state battery using a slurry is disclosed. Further, in Patent Document 2, using the aerosol position method, the ratio of the solid electrolyte is arranged higher as it is closer to the interface of the solid electrolyte, and the ratio of the active material is arranged as it is closer to the current collecting surface, and the thickness of the all-solid-state battery is increased. Disclosed is a method of manufacturing an all-solid-state battery that forms a continuous concentration gradient of electrode material in the direction.

Japanese Patent No. 5686130 Japanese Unexamined Patent Publication No. 2015-225855

However, in the production method shown in Patent Document 1, an all-solid-state battery having a small environmental load can be obtained by not using an organic solvent in the slurry, but it cannot be said that sufficient adhesion strength is obtained. In order to secure sufficient adhesion strength, it is necessary to add a large amount of binder, but since the binder inhibits lithium ion conduction and electron conduction, the charge / discharge characteristics deteriorate. In the manufacturing method shown in Patent Document 2, in the manufactured all-solid-state battery, the electrode materials such as the solid electrolyte and the active material are arranged so as to have a concentration gradient, so that ions are often diffused. Although the output performance was improved and the capacity of the battery was increased, it cannot be said that sufficient adhesion strength was obtained because the binder was not contained.

The present disclosure has been made in view of the above problems, and an object of the present disclosure is to provide an all-solid-state battery having a small environmental load and having both high adhesion strength and excellent battery characteristics.

That is, one embodiment of the all-solid-state battery according to the present disclosure is formed on a positive electrode layer including a positive electrode mixture layer containing at least a positive electrode active material and a binder formed on a positive electrode current collector and on a negative electrode current collector. A negative electrode layer including at least a negative electrode mixture layer containing at least a negative electrode active material and a binder, and a solid electrolyte layer containing at least an ionic conductive solid electrolyte arranged between the positive electrode mixture layer and the negative electrode mixture layer. The concentration of the solvent contained in at least one layer selected from the group consisting of the positive electrode mixture layer, the negative electrode mixture layer, and the solid electrolyte layer is 50 ppm or less, and the positive electrode mixture layer and the positive electrode mixture layer and The concentration of the binder contained in at least one layer selected from the negative electrode mixture layer is higher in the vicinity of the positive electrode current collector or the negative electrode current collector than in the vicinity of the solid electrolyte layer.

The present disclosure provides an all-solid-state battery having a small environmental load and having both high adhesion strength and excellent battery characteristics (for example, charge / discharge characteristics).

Schematic cross-sectional view of the all-solid-state battery according to this embodiment Schematic cross-sectional view of the positive electrode layer in this embodiment Schematic cross-sectional view of the negative electrode layer in this embodiment Schematic cross-sectional view schematically showing the state of the positive electrode layer when the all-solid-state battery according to the present embodiment is curved so that the positive electrode current collector is on the outside and the negative electrode current collector is on the inside. Schematic cross-sectional view schematically showing the state of the negative electrode layer when the all-solid-state battery according to the present embodiment is curved so that the negative electrode current collector is on the inside and the positive electrode current collector is on the outside. Schematic cross-sectional view schematically showing the state of the positive electrode layer when the all-solid-state battery according to Comparative Example 1 is curved so that the positive electrode current collector is on the outside and the negative electrode current collector is on the inside. Schematic cross-sectional view schematically showing the state of the negative electrode layer when the all-solid-state battery according to Comparative Example 2 is curved so that the negative electrode current collector is on the inside and the positive electrode current collector is on the outside. Schematic cross-sectional view schematically showing the state of the negative electrode layer in the present embodiment when the negative electrode current collector is curved to the outside and the positive electrode current collector is curved to the inside. Schematic cross-sectional view schematically showing the state of the positive electrode layer when the positive electrode current collector is inside and the negative electrode current collector is curved so as to be outside in the present embodiment. Schematic cross-sectional view schematically showing the state of the negative electrode layer when the all-solid-state battery according to Comparative Example 2 is curved so that the negative electrode current collector is on the outside and the positive electrode current collector is on the inside. Schematic cross-sectional view schematically showing the state of the positive electrode layer when the all-solid-state battery according to Comparative Example 1 is curved so that the positive electrode current collector is on the inside and the negative electrode current collector is on the outside.

Hereinafter, the all-solid-state battery according to the embodiment of the present disclosure will be described with reference to the drawings. It should be noted that the following embodiments all show specific examples of the present disclosure, and numerical values, shapes, materials, components, arrangement positions of components, connection forms, etc. are examples, and the present disclosure is limited. It's not something to do. Further, among the components in the following embodiments, the components not described in the independent claims indicating the highest level concept of the present disclosure will be described as arbitrary components.

Further, each figure is a schematic view and is not necessarily exactly illustrated. In each figure, substantially the same configuration is designated by the same reference numerals, and duplicate description may be omitted or simplified.

(Embodiment)
Hereinafter, the all-solid-state battery according to the present embodiment, and the positive electrode layer, the negative electrode layer, and the solid electrolyte layer constituting the all-solid-state battery will be described in detail with reference to the drawings.

A. All-solid-state battery The all-solid-state battery 100 according to the present embodiment will be described with reference to FIG. FIG. 1 is a schematic cross-sectional view of the all-solid-state battery 100 according to the present embodiment.

As shown in FIG. 1, the all-solid-state battery 100 according to the present embodiment includes, for example, a positive electrode current collector 6, a solid electrolyte 1, a positive electrode active material 2, and a binder 4 formed on the positive electrode current collector 6. , And the positive electrode layer 20 including the positive electrode mixture layer 21 containing the conductive auxiliary agent 5, the negative electrode current collector 7, and the solid electrolyte 1, the negative electrode active material 3, and the binder 4 formed on the negative electrode current collector 7. , And a solid electrolyte 1 having at least ionic conductivity, which is arranged between the negative electrode layer 30 including the negative electrode mixture layer 31 containing the conductive auxiliary agent 5 and the positive electrode mixture layer 21 and the negative electrode mixture layer 31. The solid electrolyte layer 40 including the solid electrolyte layer 40 is provided. The positive electrode mixture layer 21 and the negative electrode mixture layer 31 are produced on the positive electrode current collector 6 and the negative electrode current collector 7 made of metal foil, respectively.

Since the detailed description of the positive electrode layer 20, the negative electrode layer 30, and the solid electrolyte layer 40 will be described later, the description thereof will be omitted here.

A-1. Binder In the all-solid-state battery 100 according to the present embodiment, the concentration of the binder 4 contained in the positive electrode mixture layer 21 is higher in the vicinity of the positive electrode current collector 6 than in the vicinity of the solid electrolyte layer 40, and is preferable. The concentration of the binder 4 in the vicinity of the positive electrode current collector 6 is 10 times or more the concentration of the binder 4 in the vicinity of the solid electrolyte layer 40, and more preferably, the binder is not contained in the vicinity of the solid electrolyte layer 40.

Further, the concentration of the binder 4 contained in the negative electrode mixture layer 31 is higher in the vicinity of the negative electrode current collector 7 than in the vicinity of the solid electrolyte layer 40, and preferably the concentration of the binder 4 in the vicinity of the negative electrode current collector 7 is the solid electrolyte layer. It is 10 times or more the concentration of the binder 4 in the vicinity of 40, and more preferably, the binder is not contained in the vicinity of the solid electrolyte layer 40.

As a result, the adhesion between the positive electrode mixture layer 21 and the positive electrode current collector 6, and the negative electrode mixture layer 31 and the negative electrode current collector 7 is improved, and the positive electrode mixture layer 21 is charged and discharged from the all-solid battery 100. Also during expansion or contraction of the negative electrode mixture layer 31, it is possible to prevent the positive electrode mixture layer 21 and the negative electrode mixture layer 31 from being separated from the positive electrode current collector 6 and the negative electrode current collector 7, respectively. Therefore, the charge / discharge cycle life characteristics of the all-solid-state battery 100 can be improved, and high adhesion strength and excellent battery characteristics can be obtained. Here, the fact that the binder 4 is not contained means that the content of the binder 4 is 100 ppm or less.

In the present specification, the concentration is a weight-based concentration unless otherwise specified.

A-2. Conductive Auxiliary Agent In the all-solid-state battery 100 according to the present embodiment, the concentration of the conductive auxiliary agent 5 contained in the positive electrode mixture layer 21 is higher than that of the conductive auxiliary agent 5 in the vicinity of the positive electrode current collector 6 rather than in the vicinity of the solid electrolyte layer 40. The concentration is high, and preferably, the concentration of the conductive auxiliary agent 5 in the vicinity of the positive electrode current collector 6 is 10 times or more the concentration of the conductive auxiliary agent 5 in the vicinity of the solid electrolyte layer 40. When the all-solid-state battery 100 is charged and discharged, more electron conduction is performed in the vicinity of the positive electrode current collector 6 than lithium ion conduction. Therefore, it is preferable to increase the concentration of the conductive auxiliary agent 5 in the vicinity of the positive electrode current collector 6. As a result, the electron conductivity of the positive electrode layer 20 at the time of charging / discharging can be improved, and good charging / discharging characteristics can be obtained.

Further, similarly to the positive electrode layer 20, when the all-solid-state battery 100 is charged and discharged, more electron conduction is performed in the vicinity of the negative electrode current collector 7 than lithium ion conduction. Therefore, the negative electrode layer 30 in the present embodiment may have a higher concentration of the conductive auxiliary agent 5 in the vicinity of the negative electrode current collector 7 than in the vicinity of the solid electrolyte layer 40, and preferably the conductive auxiliary agent 5 in the vicinity of the negative electrode current collector 7. Is 8 times or more the concentration of the conductive auxiliary agent 5 in the vicinity of the solid electrolyte layer 40. As a result, the electron conductivity of the negative electrode layer 30 at the time of charging / discharging can be improved, and good charging / discharging characteristics can be obtained.

A-3. Solvent The all-solid-state battery 100 according to the present embodiment is a solvent contained in at least one layer selected from the group consisting of the positive electrode mixture layer 21, the negative electrode mixture layer 31, and the solid electrolyte layer 40 (specifically, the solvent). , Organic solvent) may be 50 ppm or less, preferably 30 ppm or less, and more preferably 0 ppm.

The solvent may be contained in at least one layer selected from the group consisting of the positive electrode mixture layer 21, the negative electrode mixture layer 31, and the solid electrolyte layer 40. Examples of the solvent include a non-polar solvent, a polar solvent, or a combination thereof. Examples of the non-polar solvent include heptane, xylene, toluene and the like, or a combination thereof. Examples of the polar solvent include a tertiary amine solvent, an ether solvent, a thiol solvent, an ester solvent, or a combination thereof. The tertiary amine solvent is, for example, triethylamine, the ether solvent is, for example, cyclopentyl methyl ether, the thiol solvent is, for example, ethane mercaptan, or the ester solvent is, for example, butyl butyrate. Etc., or a combination thereof.

B. Positive Electrode Layer The positive electrode layer 20 in the present embodiment will be described with reference to FIG.

FIG. 2 is a schematic cross-sectional view of the positive electrode layer 20 according to the present embodiment. In the thickness direction of the positive electrode layer 20 shown in FIG. 2, the surface opposite to the surface in contact with the positive electrode current collector 6 is the surface in contact with the solid electrolyte layer 40 (not shown in FIG. 2).

The positive electrode layer 20 in the present embodiment includes, for example, a positive electrode current collector 6 made of a metal foil and a positive electrode mixture layer 21 formed on the positive electrode current collector 6.

B-1. Positive electrode mixture layer The positive electrode mixture layer 21 may contain at least the positive electrode active material 2 and the binder 4, and in the all-solid-state battery 100 according to the present embodiment, for example, as shown in FIGS. 1 and 2. The positive electrode mixture layer 21 contains a solid electrolyte 1, a positive electrode active material 2, a binder 4, and a conductive additive 5.

B-1-1. Binder The binder 4 in the present embodiment will be described. The binder 4 in the present embodiment is not particularly limited, but specifically, butadiene rubber, isoprene rubber, styrene-butadiene rubber (SBR), styrene-butadiene-styrene (SBS), styrene-ethylene-butadiene-styrene ( SEBS), ethylene-propylene, butyl rubber, chloroprene rubber, acrylonitrile-butadiene rubber, acrylic rubber, silicone rubber, fluororubber, urethane rubber and other synthetic rubbers, or PVDF (polyvinylidene fluoride), PVDF-HFP (polyvinylidene fluoride). Ride-hexafluoropropylene copolymer), polyimide, polyamide, polyamideimide, polyvinyl alcohol, CM (chlorinated polyethylene) and the like. The binder 4 may be used alone or in combination of two or more.

The concentration of the binder 4 contained in the positive electrode mixture layer 21 in the present embodiment is higher in the vicinity of the positive electrode current collector 6 than in the vicinity of the solid electrolyte layer 40. Specifically, as shown in FIG. 2, in an arbitrary region A1 near the positive electrode current collector 6 and an arbitrary region A2 near the solid electrolyte layer 40, the concentration of the binder 4 is higher in the region A1 than in the region A2. Is high, preferably the concentration of the binder 4 contained in the region A1 is 10 times or more the concentration of the binder 4 contained in the region A2, and more preferably the binder 4 is not contained in the region A2.

As described above, by including the binder 4 so as to have a concentration gradient in the thickness direction of the positive electrode mixture layer 21, the lithium ion conductivity during charging and discharging is excellent, and the positive electrode current collector 6 and the positive electrode mixture layer 21 are combined. High adhesion strength can be obtained between them.

Here, the fact that the binder 4 is not contained means that the content of the binder 4 is 100 ppm or less.

The arbitrary region A1 in the vicinity of the positive electrode current collector 6 and the arbitrary region A2 in the vicinity of the solid electrolyte layer 40 may extend over the entire surface in contact with the positive electrode current collector 6 and the solid electrolyte layer 40, respectively, and may partially extend. It may be spread. Further, the regions A1 and A2 shown in FIG. 2 may overlap each other or may be independently independent of each other.

Hereinafter, the durability and battery performance of the all-solid-state battery due to the difference in the concentration gradient of the binder 4 in the positive electrode mixture layer 21 will be described.

In the all-solid-state battery 100 according to the present embodiment, the concentration of the binder 4 in the positive electrode mixture layer 21 is higher in the vicinity of the positive electrode current collector 6 than in the vicinity of the solid electrolyte layer 40 of the positive electrode mixture layer 21. On the other hand, in the all-solid-state battery according to Comparative Example 1, the binder 4 is substantially uniformly dispersed in the entire positive electrode mixture layer 21, and the concentration of the binder 4 in the positive electrode mixture layer 21 is uniform.

FIG. 4 schematically shows a state of the positive electrode layer 20 when the all-solid-state battery 100 according to the present embodiment is curved so that the positive electrode current collector 6 is on the outside and the negative electrode current collector 7 is on the inside. It is a schematic cross-sectional view shown in. At this time, the positive electrode layer 20 is bent so that the positive electrode current collector 6 has the longest arc. Generally, the positive electrode current collector 6 made of a metal foil is difficult to stretch, so that the positive electrode mixture layer 21 and the positive electrode current collector 6 are easily peeled off.

As described above, in the positive electrode mixture layer 21 of the present embodiment, the concentration of the binder 4 in the vicinity of the positive electrode current collector 6 is higher than that in the vicinity of the solid electrolyte layer 40. Therefore, the adhesion between the positive electrode current collector 6 and the positive electrode mixture layer 21 can be improved. Therefore, as shown in FIG. 4, even if the all-solid-state battery 100 is curved with the positive electrode current collector 6 on the outside, the positive electrode current collector 6 and the positive electrode mixture layer 21 are difficult to peel off, so that the positive electrode layer 20 The electron conductivity can be improved.

On the other hand, FIG. 6 illustrates the state of the positive electrode layer 20 when the all-solid-state battery according to Comparative Example 1 is curved so that the positive electrode current collector 6 is on the outside and the negative electrode current collector 7 is on the inside. It is a schematic cross-sectional view. At this time, the positive electrode layer 20 is bent so that the positive electrode current collector 6 has the longest arc. Generally, the positive electrode current collector 6 made of a metal foil is difficult to stretch, so that the positive electrode mixture layer 21 and the positive electrode current collector 6 are easily peeled off.

As shown in FIG. 6, in the positive electrode layer 20, since the binder 4 is substantially uniformly dispersed in the entire positive electrode mixture layer 21, the adhesion between the positive electrode current collector 6 and the positive electrode mixture layer 21 is not improved. Therefore, as shown in FIG. 6, when the all-solid-state battery is curved with the positive electrode current collector 6 facing outward, the adhesion between the positive electrode current collector 6 and the positive electrode mixture layer 21 is not sufficient, so that the positive electrode current collector is not sufficient. The body 6 and the positive electrode mixture layer 21 are easily peeled off, and the electron conduction path in the positive electrode layer 20 is easily cut.

Further, FIG. 9 shows a state of the positive electrode layer 20 when the all-solid-state battery 100 according to the present embodiment is curved so that the positive electrode current collector 6 is on the inside and the negative electrode current collector 7 is on the outside. It is schematic cross-sectional view to explain. At this time, the shape of the positive electrode layer 20 changes to be substantially concave due to the addition of curvature.

As described above, the positive electrode layer 20 in the present embodiment has a higher concentration of the binder 4 in the vicinity of the positive electrode current collector 6 than in the vicinity of the solid electrolyte layer 40. Therefore, the adhesion between the positive electrode current collector 6 and the positive electrode mixture layer 21 can be improved. Therefore, as shown in FIG. 9, even if the all-solid-state battery 100 is curved with the positive electrode current collector 6 inside to give curvature to the positive electrode layer 20, the positive electrode mixture is used to change the shape of the positive electrode current collector 6. Since the layer 21 can easily follow, the electron conductivity of the positive electrode layer 20 can be improved.

From FIGS. 4 and 9, by applying the configuration of the predetermined concentration gradient of the binder 4 in the present embodiment to the positive electrode layer 20, the positive electrode layer 20 can maintain good charge / discharge characteristics of the all-solid-state battery 100. It is possible to increase the durability against external force and increase the degree of design freedom when the all-solid-state battery 100 is applied to various devices.

On the other hand, FIG. 11 illustrates the state of the positive electrode layer 20 when the all-solid-state battery according to Comparative Example 1 is curved so that the positive electrode current collector 6 is on the inside and the negative electrode current collector 7 is on the outside. It is a schematic cross-sectional view. At this time, the shape of the positive electrode layer 20 changes to be substantially concave due to the addition of curvature.

As shown in FIG. 11, in the positive electrode layer 20, since the binder 4 is substantially uniformly dispersed in the entire positive electrode mixture layer 21, the adhesion between the positive electrode current collector 6 and the positive electrode mixture layer 21 is not improved. Therefore, as shown in FIG. 11, when the all-solid-state battery provided with the positive electrode layer 20 of Comparative Example 1 is curved with the positive electrode current collector 6 inside, the positive electrode current collector 6 and the positive electrode mixture layer 21 are in close contact with each other. Since the properties are not sufficient, it becomes difficult for the positive electrode mixture layer 21 to follow the shape change of the positive electrode current collector 6, and the electron conduction path in the positive electrode layer 20 is easily cut.

From FIGS. 6 and 11, when the binder 4 is dispersed substantially uniformly in the positive electrode mixture layer 21, the durability of the positive electrode layer 20 against an external force is lowered, and the battery characteristics such as the charge / discharge characteristics of the all-solid-state battery are lowered. Tend.

B-1-2. Conductive Auxiliary Agent The conductive auxiliary agent 5 in the present embodiment will be described below.

The conductive auxiliary agent 5 in the present embodiment is not particularly limited as long as it improves the electron conductivity of the positive electrode mixture layer 21, and examples thereof include acetylene black, ketjen black, and carbon fiber. The conductive auxiliary agent 5 may be used alone or in combination of two or more.

As shown in FIG. 1, in the all-solid-state battery 100 according to the present embodiment, the conductive additive 5 may be contained in the positive electrode mixture layer 21. As a result, the electron conductivity in the positive electrode mixture layer 21 can be increased, so that the electron conduction path in the positive electrode mixture layer 21 can be secured, and the internal resistance of the all-solid-state battery can be reduced. Therefore, the amount of current that can be conducted through the electron conduction path increases, and the charge / discharge characteristics of the all-solid-state battery are improved.

In the present embodiment, in addition to the concentration of the binder 4, the concentration of the conductive additive 5 is also configured to have a predetermined concentration gradient in the thickness direction of the positive electrode mixture layer 21. That is, in the all-solid-state battery 100 according to the present embodiment, the concentration of the conductive auxiliary agent 5 contained in the positive electrode mixture layer 21 may be higher in the vicinity of the positive electrode current collector 6 than in the vicinity of the solid electrolyte layer 40. ..

Specifically, as shown in FIG. 2, in an arbitrary region A3 near the positive electrode current collector 6 and an arbitrary region A4 near the solid electrolyte layer 40, the conductive auxiliary agent 5 is more in the region A3 than in the region A4. The concentration of the conductive auxiliary agent 5 contained in the region A3 is preferably 10 times or more the concentration of the conductive auxiliary agent 5 contained in the region A4. This is to improve the electron conductivity between the positive electrode current collector 6 and the positive electrode mixture layer 21.

The regions A3 and A4 shown in FIG. 2 may overlap each other or may be independently independent of each other.

B-1--3. Positive Electrode Active Material The positive electrode active material 2 in the present embodiment will be described below.

The positive electrode active material 2 refers to a substance in which lithium (Li) is inserted or removed from the crystal structure at a potential higher than that of the negative electrode layer 30, and oxidation or reduction is performed accordingly. The type of the positive electrode active material 2 is appropriately selected according to the type of the all-solid-state battery 100, and examples thereof include an oxide active material and a sulfide active material.

As the positive electrode active material 2 in the present embodiment, for example, an oxide active material (lithium-containing transition metal oxide) is used. As the oxide active material, for example, LiCoO ₂ , LiNiO ₂ , LiMn ₂ O ₄ , LiCoPO ₄ , LiNiPO ₄ , LiFePO ₄ , LiMnPO ₄ , by substituting the transition metal of these compounds with one or two different elements. Examples thereof include the obtained compounds. Examples of the compound obtained by substituting the transition metal of the above compound with one or two different elements include LiNi _1/3 Co _1/3 Mn _1/3 O ₂ , LiNi _0.8 Co _0.15 Al _0.05. Known materials such as O ₂ and LiNi _0.5 Mn _1.5 O _{2 are used.} The positive electrode active material 2 may be used alone or in combination of two or more.

Examples of the shape of the positive electrode active material 2 include a particle shape and a thin film shape. When the positive electrode active material 2 is in the form of particles, its average particle size (D ₅₀ ) is, for example, in the range of 50 nm or more and 50 μm or less, and preferably in the range of 1 μm or more and 15 μm or less. This is because if the average particle size of the positive electrode active material 2 is too small, the handleability may deteriorate, while if the average particle size is too large, it may be difficult to obtain a flat positive electrode layer 20. Because there is. The "average particle size" in the present specification means a volume-based average diameter measured by a laser analysis and a scattering type particle size distribution measuring device.

The content of the positive electrode active material 2 in the positive electrode mixture layer 21 is not particularly limited, but is preferably in the range of 40% by weight or more and 99% by weight or less, and particularly 70% by weight or more and 95% by weight or less. % Or less is preferable.

The surface of the positive electrode active material 2 may be coated with a coat layer. This is because the reaction between the positive electrode active material 2 (for example, the oxide active material) and the solid electrolyte 1 (for example, the sulfide solid electrolyte) can be suppressed. Examples of the material of the coat layer include Li ion conductive oxides such as _{LiNbO 3} , Li ₃ PO _{4, and LiPON.} The average thickness of the coat layer is, for example, preferably in the range of 1 nm or more and 20 nm or less, and more preferably in the range of 1 nm or more and 10 nm or less.

The ratio of the positive electrode active material 2 and the solid electrolyte 1 contained in the positive electrode mixture layer 21 is preferably in the range of positive electrode active material / solid electrolyte = 1 or more and 19 or less in terms of weight, and more preferably 70 /. It is in the range of 30 or more and 19 or less. This is to secure both the lithium ion conduction path and the electron conduction path in the positive electrode mixture layer 21.

B-1-4. Solid Electrolyte Hereinafter, the solid electrolyte 1 in the present embodiment will be described.

As shown in FIG. 1, the positive electrode mixture layer 21 in the present embodiment contains the solid electrolyte 1 in addition to the positive electrode active material 2 and the binder 4. The solid electrolyte 1 may be appropriately selected according to the conduction ion species (for example, lithium ion), and can be broadly divided into, for example, a sulfide-based solid electrolyte and an oxide-based solid electrolyte.

The type of the sulfide-based solid electrolyte in the present embodiment is not particularly limited, but Li ₂ S-SiS ₂ , LiI-Li ₂ S-SiS ₂ , LiI-Li _{2 SP 2} S ₅ , LiI-Li ₂ S. _{-P 2 O 5, LiI-Li} 3 PO 4 -P 2 S 5, Li 2 S-P 2 S 5 , and the like. In particular, it preferably contains Li, P and S. This is because the lithium ion conductivity is excellent. The sulfide-based solid electrolyte may be used alone or in combination of two or more. Further, the sulfide solid electrolyte may be crystalline, amorphous, or glass ceramics. The above description of "Li ₂ SP ₂ S ₅ " means a sulfide solid electrolyte using a raw material composition containing _{Li 2} S and P ₂ S _{5, and the same applies to other descriptions.}

In this embodiment, one form of the sulfide-based solid electrolyte is a sulfide glass ceramics containing Li ₂ S and _P 2 _{S 5,} the proportion of Li ₂ S and _P 2 _{S 5} is Li molar basis ₂ S / P ₂ S ₅ = 70/30 or more and 4 or less is preferable, and more preferably 3 or more and 4 or less. This is because the crystal structure has high ionic conductivity while maintaining the lithium concentration that affects the battery characteristics. Furthermore, to react with a binder, in order to ensure the amount of P ₂ S ₅ for coupling.

Examples of the shape of the sulfide solid electrolyte in the present embodiment include a particle shape such as a true spherical shape and an elliptical spherical shape, and a thin film shape. When the sulfide solid electrolyte material has a particle shape, its average particle size (D ₅₀ ) is not particularly limited, but is preferably 40 μm or less, more preferably 20 μm or less, and 10 μm or less. Is more preferable. This is because it becomes easy to improve the filling rate in the positive electrode layer. On the other hand, the average particle size is preferably 0.01 μm or more, and more preferably 0.1 μm or more. The average particle size can be determined by, for example, a particle size distribution meter.

The oxide-based solid electrolyte in the present embodiment will be described. The type of oxide-based solid electrolyte is not particularly limited, but LiPON, Li ₃ PO ₄ , Li ₂ SiO ₂ , Li ₂ SiO ₄ , Li _0.5 La _0.5 TiO ₃ , Li _1.3 Al _0.3 Ti. _Examples thereof include 0.7 (PO ₄ ) ₃ , La _0.51 Li _0.34 TiO _0.74 , Li _1.5 Al _0.5 Ge _1.5 (PO ₄ ) _3. The oxide-based solid electrolyte may be used alone or in combination of two or more.

B-2. Positive electrode current collector The positive electrode layer 20 in the present embodiment includes, for example, a positive electrode current collector 6 made of a metal foil. The positive electrode current collector 6 includes, for example, a foil-like body, a plate-like body, or a mesh-like body made of aluminum, gold, platinum, zinc, copper, SUS, nickel, tin, titanium, or an alloy of two or more of these. The body etc. are used.

Further, the thickness, shape and the like of the positive electrode current collector 6 may be appropriately selected depending on the use of the all-solid-state battery.

C. Negative electrode layer The negative electrode layer 30 in the present embodiment will be described with reference to FIG. FIG. 3 is a schematic cross-sectional view of the negative electrode layer 30 according to the present embodiment. In the thickness direction of the negative electrode layer 30 shown in FIG. 3, the surface opposite to the surface in contact with the negative electrode current collector 7 is the surface in contact with the solid electrolyte layer 40 (not shown in FIG. 3).

The negative electrode layer 30 in the present embodiment includes, for example, a negative electrode current collector 7 made of a metal foil and a negative electrode mixture layer 31 formed on the negative electrode current collector 7.

C-1. Negative electrode mixture layer The negative electrode mixture layer 31 may contain at least the negative electrode active material 3 and the binder 4, and in the all-solid-state battery 100 according to the present embodiment, for example, as shown in FIGS. 1 and 3. The negative electrode mixture layer 31 contains a solid electrolyte 1, a negative electrode active material 3, a binder 4, and a conductive additive 5.

C-1-1. Binder The type of the binder 4 is the same as that described above in the section “B. Positive electrode layer”, and thus the description thereof is omitted here.

The concentration of the binder 4 contained in the negative electrode mixture layer 31 in the present embodiment is higher in the vicinity of the negative electrode current collector 7 than in the vicinity of the solid electrolyte layer 40. Specifically, as shown in FIG. 3, in an arbitrary region B1 near the negative electrode current collector 7 and an arbitrary region B2 near the solid electrolyte layer 40, the concentration of the binder 4 is higher in the region B1 than in the region B2. It is high, preferably the concentration of the binder 4 contained in the region B1 is 10 times or more the concentration of the binder 4 contained in the region B2, and more preferably the binder 4 is not contained in the region B2.

As described above, by including the binder 4 so as to have a concentration gradient in the thickness direction of the negative electrode mixture layer 31, the lithium ion conductivity during charging and discharging is excellent, and the negative electrode current collector 7 and the negative electrode mixture layer 31 are combined. High adhesion strength can be obtained between them.

Here, the fact that the binder 4 is not contained means that the content of the binder 4 is 100 ppm or less.

The arbitrary region B1 in the vicinity of the negative electrode current collector 7 and the arbitrary region B2 in the vicinity of the solid electrolyte layer 40 may extend over the entire surface in contact with the negative electrode current collector 7 and the solid electrolyte layer 40, respectively, and may partially extend. It may be spread. Further, the regions B1 and B2 shown in FIG. 3 may overlap each other or may be independently independent of each other.

Hereinafter, the durability and battery performance of the all-solid-state battery due to the difference in the concentration gradient of the binder 4 in the negative electrode mixture layer 31 will be described.

In the all-solid-state battery 100 according to the present embodiment, the concentration of the binder 4 in the negative electrode mixture layer 31 is higher in the vicinity of the negative electrode current collector 7 than in the vicinity of the solid electrolyte layer 40 of the negative electrode mixture layer 31. On the other hand, in the all-solid-state battery according to Comparative Example 2, the binder 4 is substantially uniformly dispersed in the entire negative electrode mixture layer 31, and the concentration of the binder 4 in the negative electrode mixture layer 31 is uniform.

FIG. 5 schematically shows a state of the negative electrode layer 30 when the all-solid-state battery 100 according to the present embodiment is curved so that the negative electrode current collector 7 is on the inside and the positive electrode current collector 6 is on the outside. It is a schematic cross-sectional view shown in. At this time, the shape of the negative electrode layer 30 changes to be substantially concave due to the addition of curvature.

As described above, the negative electrode layer 30 in the present embodiment has a higher concentration of the binder 4 in the vicinity of the negative electrode current collector 7 than in the vicinity of the solid electrolyte layer 40. Therefore, the adhesion between the negative electrode current collector 7 and the negative electrode mixture layer 31 can be improved. Therefore, as shown in FIG. 5, even if the all-solid-state battery 100 is curved with the negative electrode current collector 7 inside and the positive electrode layer 20 is curved, the negative electrode mixture layer 31 changes the shape of the negative electrode current collector 7. Is easy to follow, so that the electron conductivity of the negative electrode layer 30 can be improved.

On the other hand, FIG. 7 schematically shows the state of the negative electrode layer 30 when the all-solid-state battery according to Comparative Example 2 is curved so that the negative electrode current collector 7 is on the inside and the positive electrode current collector 6 is on the outside. It is a schematic cross-sectional view shown in. At this time, the shape of the negative electrode layer 30 changes to be substantially concave due to the addition of curvature.

As shown in FIG. 7, in the negative electrode layer 30, since the binder 4 is substantially uniformly dispersed in the entire negative electrode mixture layer 31, the adhesion between the negative electrode current collector 7 and the negative electrode mixture layer 31 is not sufficient. .. Therefore, as shown in FIG. 7, when the all-solid-state battery provided with the negative electrode layer 30 of Comparative Example 2 is curved with the negative electrode current collector 7 inside, the negative electrode current collector 7 and the negative electrode mixture layer 31 come into close contact with each other. Since the properties are not sufficient, it becomes difficult for the negative electrode mixture layer 31 to follow the shape change of the negative electrode current collector 7, and the electron conduction path in the negative electrode layer 30 is easily cut.

Further, FIG. 8 shows a state of the negative electrode layer 30 when the all-solid-state battery 100 according to the present embodiment is curved so that the negative electrode current collector 7 is on the outside and the positive electrode current collector 6 is on the inside. It is schematic cross-sectional view to explain. At this time, the negative electrode layer 30 is bent so that the negative electrode current collector 7 has the longest arc. Since the negative electrode current collector 7 made of a metal foil is generally difficult to stretch, the negative electrode mixture layer 31 and the negative electrode current collector 7 are easily peeled off.

As described above, in the negative electrode mixture layer 31 in the present embodiment, the concentration of the binder 4 in the vicinity of the negative electrode current collector 7 is higher than that in the vicinity of the solid electrolyte layer 40. Therefore, the adhesion between the negative electrode current collector 7 and the negative electrode mixture layer 31 can be improved. Therefore, as shown in FIG. 8, even if the all-solid-state battery 100 is curved with the negative electrode current collector 7 on the outside, the negative electrode current collector 7 and the negative electrode mixture layer 31 are difficult to peel off, so that the negative electrode layer 30 The electron conductivity can be improved.

From FIGS. 5 and 8, by applying the configuration of the predetermined concentration gradient of the binder 4 in the present embodiment to the negative electrode layer 30, the negative electrode layer 30 can maintain good charge / discharge characteristics of the all-solid-state battery 100. It is possible to increase the durability against external force and increase the degree of design freedom when the all-solid-state battery 100 is applied to various devices.

On the other hand, FIG. 10 illustrates the state of the negative electrode layer 30 when the all-solid-state battery according to Comparative Example 2 is curved so that the negative electrode current collector 7 is on the outside and the positive electrode current collector 6 is on the inside. It is a schematic cross-sectional view. At this time, the negative electrode layer 30 is bent so that the negative electrode current collector 7 has the longest arc. Since the negative electrode current collector 7 made of a metal foil is generally difficult to stretch, the negative electrode mixture layer 31 and the negative electrode current collector 7 are easily peeled off.

As shown in FIG. 10, in the negative electrode layer 30, since the binder 4 is substantially uniformly dispersed in the entire negative electrode mixture layer 31, the adhesion between the negative electrode current collector 7 and the negative electrode mixture layer 31 is not sufficient. .. Therefore, as shown in FIG. 10, when the all-solid-state battery is curved so that the negative electrode current collector 7 is on the outside and the positive electrode current collector 6 is on the inside, the negative electrode current collector 7 and the negative electrode mixture layer 31 are formed. Since the adhesion is not sufficient, the negative electrode current collector 7 and the negative electrode mixture layer 31 are easily peeled off, and the electron conduction path in the negative electrode layer 30 is easily cut.

From FIGS. 7 and 10, when the binder 4 is dispersed substantially uniformly in the negative electrode mixture layer 31, the durability of the negative electrode layer 30 against an external force is lowered, and the battery characteristics such as the charge / discharge characteristics of the all-solid-state battery are lowered. Tend.

In the present embodiment shown in FIGS. 1 to 3, when the all-solid-state battery 100 is connected to an external device and the all-solid-state battery 100 is curved for the convenience of design, the negative electrode of the negative electrode layer 30 is collected. When the body 7 is on the outside and the positive electrode current collector 6 of the positive electrode layer 20 is on the inside and curved, the positive electrode current collector 6 of the positive electrode layer 20 is on the outside and the negative electrode current collector 7 of the negative electrode layer 30 is on the inside. Better than bending.

Generally, the negative electrode active material 3 contained in the negative electrode layer 30 is easily stretched, while the positive electrode active material 2 contained in the positive electrode layer 20 is not easily stretched. Therefore, it is easier to follow the shape change when the negative electrode layer 30 is curved outward, and the region near the positive electrode current collector 6 in the positive electrode mixture layer 21 and the region near the negative electrode current collector 7 in the negative electrode mixture layer 31. It is possible to reduce the amount of the binder 4 in the above. As a result, it is possible to suppress a decrease in battery capacity and an increase in internal resistance due to the binder 4, and excellent battery characteristics such as improvement in charge / discharge characteristics of the all-solid-state battery 100 can be obtained.

C-1-2. Conductive Auxiliary Agent The conductive auxiliary agent 5 in the present embodiment will be described below. Since the types of the conductive auxiliary agent 5 are the same as those described above in the section “B. Positive electrode layer”, the description thereof will be omitted here.

As shown in FIG. 1, in the all-solid-state battery 100 according to the present embodiment, the negative electrode mixture layer 31 may contain the conductive auxiliary agent 5. As a result, the electron conductivity in the negative electrode mixture layer 31 can be increased, so that the electron conduction path in the negative electrode mixture layer 31 can be secured, and the internal resistance of the all-solid-state battery 100 can be lowered. .. Therefore, the amount of current that can be conducted through the electron conduction path increases, and the charge / discharge characteristics of the all-solid-state battery 100 are improved.

In the present embodiment, in addition to the concentration of the binder 4, the concentration of the conductive additive 5 is also configured to have a predetermined concentration gradient in the thickness direction of the negative electrode mixture layer 31. That is, in the all-solid-state battery 100 according to the present embodiment, the concentration of the conductive auxiliary agent 5 contained in the negative electrode mixture layer 31 may be higher in the vicinity of the negative electrode current collector 7 than in the vicinity of the solid electrolyte layer 40. ..

Specifically, as shown in FIG. 3, in an arbitrary region B3 near the negative electrode current collector 7 and an arbitrary region B4 near the solid electrolyte layer, the concentration of the conductive auxiliary agent 5 in the region B3 is higher than that in the region B4. The concentration of the conductive auxiliary agent 5 contained in the region B3 is preferably 8 times or more the concentration of the conductive auxiliary agent 5 contained in the region B4. This is to improve the electron conductivity between the negative electrode current collector 7 and the negative electrode mixture layer 31.

When the all-solid-state battery 100 is charged and discharged, more electron conduction is performed in the vicinity of the negative electrode current collector 7 than lithium ion conduction. Therefore, in the negative electrode layer 30 in the present embodiment, the concentration of the conductive auxiliary agent 5 in the vicinity of the negative electrode current collector 7 is higher than that in the vicinity of the solid electrolyte layer 40, so that the negative electrode mixture layer 31 in the vicinity of the negative electrode current collector 7 is increased. The internal resistance of the can be reduced. Thereby, the output characteristics of the all-solid-state battery 100 can be improved.

The regions B3 and B4 may overlap each other or may be independently independent of each other.

C-1-3. Negative electrode active material The negative electrode active material 3 in the present embodiment will be described. The negative electrode active material 3 refers to a material in which lithium is inserted or removed from the crystal structure at a potential lower than that of the positive electrode layer 20, and oxidation or reduction is performed accordingly.

Examples of the negative electrode active material 3 in the present embodiment include easily alloyed metals with lithium such as lithium, indium, tin and silicon, carbon materials such as hard carbon and graphite, or Li ₄ Ti ₅ O ₁₂ and SiO _x. Known materials such as oxide active materials such as are used. Further, a complex or the like in which the above-mentioned negative electrode active material is appropriately mixed can also be used.

The ratio of the negative electrode active material 3 to the solid electrolyte 1 contained in the negative electrode mixture layer 31 is preferably in the range of negative electrode active material / solid electrolyte = 40/60 or more and 19 or less in terms of weight, and more preferably. It is in the range of 1 or more and 85/15 or less. This is to secure both the lithium ion conduction path and the electron conduction path in the negative electrode mixture layer 31.

C-1-4. Solid Electrolyte The solid electrolyte 1 is the same as that described above in the section “B. Positive electrode layer”, and thus the description thereof is omitted here.

C-2. Negative electrode current collector The negative electrode layer 30 in the present embodiment includes, for example, a negative electrode current collector 7 made of a metal foil. The negative electrode current collector 7 includes, for example, a foil-like body, a plate-like body, a mesh-like body made of SUS, gold, platinum, zinc, copper, nickel, titanium, tin, or an alloy of two or more of these. Is used.

Further, the thickness, shape and the like of the negative electrode current collector 7 may be appropriately selected depending on the use of the all-solid-state battery.

D. Solid Electrolyte Layer The solid electrolyte layer 40 in the present embodiment will be described. The solid electrolyte layer 40 contains at least the solid electrolyte 1 having lithium ion conductivity, and may contain the binder 4 in order to increase the adhesion strength between the solid electrolytes 1.

D-1. Binder The type of the binder 4 is the same as that described above in the section “B. Positive electrode layer”, and thus the description thereof is omitted here.

Regarding the content of the binder 4 in the solid electrolyte layer 40, the binder 4 is preferably contained in an amount of 1 wt% or less, more preferably 0.5 wt% or less, and further preferably the binder 4 in an amount of 1 wt% or less of the solid electrolyte 1. There is no such thing. This is because the binder 4 inhibits the lithium ion conduction of the solid electrolyte layer 40 and deteriorates the charge / discharge characteristics of the all-solid-state battery 100. Here, the fact that the binder 4 is not contained means that the content of the binder 4 is 100 ppm or less.

D-2. Solid Electrolyte The solid electrolyte 1 is the same as that described above in the section “B. Positive electrode layer”, and thus the description thereof is omitted here.

E. Other Configuration Although not shown, the all-solid-state battery 100 according to the present embodiment is attached by welding terminals (metal positive electrode leads) to the surface of the positive electrode current collector 6 opposite to the positive electrode mixture layer 21. A terminal (metal negative electrode lead) is welded and attached to the surface of the negative electrode current collector 7 on the side opposite to the negative electrode mixture layer 31. The all-solid-state battery 100 thus obtained or a group of batteries obtained by connecting a plurality of the all-solid-state batteries is housed in a battery case, and the positive electrode lead and the negative electrode lead are led out to the outside of the battery case to obtain a battery. It may be configured to seal the case.

Here, as the battery case, for example, a bag made of an aluminum laminated film or the like, a case made of metal (for example, SUS, iron, aluminum, etc.) or a case made of resin of any shape is used.

F. Manufacturing method F-1. Method for manufacturing an all-solid-state battery In the method for manufacturing an all-solid-state battery 100 according to the present embodiment, for example, a film forming step for preparing a positive electrode layer 20, a negative electrode layer 30, and a solid electrolyte layer 40, and a positive electrode layer 20 prepared. A laminating step of aligning or laminating the negative electrode layer 30 and the solid electrolyte layer 40 so that the solid electrolyte layer 40 is arranged between the positive electrode mixture layer 21 and the negative electrode mixture layer 31, and a pressing step of pressing. , Have.

The film forming process will be described later in the section of the manufacturing method of each layer.

In the pressing step, the positive electrode layer 20, the negative electrode layer 30, and the solid electrolyte layer 40 obtained in the film forming step are arranged so that the solid electrolyte layer 40 is arranged between the positive electrode mixture layer 21 and the negative electrode mixture layer 31. The all-solid-state battery 100 is obtained by pressing from the outside of the positive electrode current collector 6 and the negative electrode current collector 7 at, for example, 4 ton / cm ^2. The filling rate of the positive electrode mixture layer 21, the negative electrode mixture layer 31, and the solid electrolyte layer 40 is increased by the pressing step. By increasing the filling rate, the lithium ion conductivity and the electron conductivity can be improved in the positive electrode mixture layer 21, the negative electrode mixture layer 31, and the solid electrolyte layer 40, and good battery characteristics can be obtained. be.

The filling rate means the ratio of the volume of all substances occupied by the object to the apparent volume of the object. For example, the filling rate of the positive electrode mixture layer 21 means the ratio of the volume of all the substances constituting the positive electrode mixture layer 21 to the apparent volume of the positive electrode mixture layer 21. Further, the press pressure is ^{not limited to 4 ton / cm 2} , and a press pressure in which the filling rate of each layer can be adjusted within a desired range can be appropriately selected.

F-2. Method for manufacturing the positive electrode layer As the method for manufacturing the positive electrode layer 20 in the present embodiment, for example, the following two methods can be mentioned.

(1) For the positive electrode layer 20 in the present embodiment, for example, a solid electrolyte 1, a positive electrode active material 2, a binder 4 and a conductive auxiliary agent 5 are dispersed in an organic solvent to prepare a slurry, and the obtained slurry is collected as a positive electrode. A coating step of applying to the surface of the electric body 6, a drying and firing step of heating and drying the obtained coating film to remove an organic solvent, and a press for pressing the dry coating film formed on the positive electrode current collector 6. It can be produced by a manufacturing method including a step (the film forming step described above).

Further, in the present production method, a plurality of slurries containing the solid electrolyte 1, the positive electrode active material 2, the binder 4, and the conductive auxiliary agent 5 as needed, and having different concentrations of the binder 4 and the conductive auxiliary agent 5 are prepared. The positive electrode layer 20 according to the present embodiment is also produced by repeatedly applying the slurry having the highest concentration of the binder 4 and the concentration of the conductive auxiliary agent 5 to the positive electrode current collector 6 and drying the slurry. be able to.

The method for applying the slurry is not particularly limited, but may be a blade coater, a gravure coater, a dip coater, a reverse coater, a roll knife coater, a wire bar coater, a slot die coater, an air knife coater, a curtain coater, an extrusion coater, or the like. A known coating method of the combination of the above can be adopted.

Since the organic solvent for preparing the slurry is the same as that described above in the section “A-3. Solvent”, the description thereof is omitted here.

The concentration of the organic solvent contained in the positive electrode mixture layer 21 in the present embodiment may be 50 ppm or less, preferably 30 ppm or less, and more preferably 0 ppm.

The method for measuring the organic solvent is not particularly limited, and examples thereof include gas chromatography, mass change method, and the like.

(2) Further, in the positive electrode layer 20 in the present embodiment, for example, after uniformly arranging the binder 4 and the conductive auxiliary agent 5 on the surface of the positive electrode current collector 6, the solid electrolyte 1 and the positive electrode active material are arranged on the surface thereof. By a manufacturing method (deposition step) including a laminating step of uniformly laminating a positive electrode mixture obtained by mixing 2 and, if necessary, a binder 4 and a conductive auxiliary agent 5, and a pressing step of pressing the obtained laminate. Can also be produced.

The drying and firing steps in the above-mentioned two production methods are not particularly limited, and known drying and firing steps may be adopted. The pressing process is not particularly limited, and a known pressing process may be adopted.

The temperature of the drying and firing steps is not particularly limited, and examples thereof include a temperature in the range of room temperature to 500 ° C. The press pressure is not particularly limited as long as a predetermined filling rate or the like of the positive electrode mixture layer 21 can be achieved.

F-3. Method for manufacturing the negative electrode layer The negative electrode layer 30 of the present embodiment can be manufactured in the same manner as the positive electrode layer 20 described above, except that the material used is changed for the negative electrode layer 30.

The concentration of the solvent contained in the negative electrode mixture layer 31 in the present embodiment may be 50 ppm or less, preferably 30 ppm or less, and more preferably 0 ppm.

The method for measuring the organic solvent is as described above.

F-4. Method for Producing Solid Electrolyte Layer In the solid electrolyte layer 40 in the present embodiment, for example, the solid electrolyte 1 and, if necessary, the binder 4 are dispersed in an organic solvent to prepare a slurry, and the obtained slurry is placed on a substrate. It can be produced in the same manner as the above-mentioned positive electrode layer 20 except that it has a step of applying and a step of peeling off the base material after the pressing step.

When the slurry is applied on a substrate and dried to prepare a solid electrolyte membrane, the type of organic solvent used for preparing the slurry is the same as that described above in the section "A-3. Solvent". The description here will be omitted. The organic solvent used for preparing the slurry is not particularly limited as long as it does not adversely affect the performance of the solid electrolyte, and examples thereof include hydrocarbon-based organic solvents such as heptane, toluene, and hexane, which are preferable. A hydrocarbon-based organic solvent that has been dehydrated to reduce the water content is used.

The base material is not particularly limited as long as a solid electrolyte membrane can be formed on the base material, and a base material having film-like flexibility, a hard base material, or the like can be used, for example. A base material such as Teflon (registered trademark) or polyethylene terephthalate (PET) film can be used.

The concentration of the solvent contained in the solid electrolyte layer 40 in the present embodiment may be 50 ppm or less, and may be 0 ppm.

The method for measuring the organic solvent is as described above.

The present disclosure is not limited to the above embodiment. The above-described embodiment is an example, and within the scope of the claims of the present disclosure, any one having substantially the same configuration as the technical idea and exhibiting the same effect and effect may be used. It is included in the technical scope of the present disclosure.

Examples of the present embodiment will be described below, but the embodiments of the present disclosure are not limited to these examples. Unless otherwise specified, each example was carried out in a glove box whose dew point was controlled to −45 ° C. or lower, or in a dry room.

(Preparation of solid electrolyte)
First, a solid electrolyte Li ₂ SP ₂ S ₅ was prepared. Li ₂ S and P ₂ S ₅ were weighed so that Li ₂ S: P ₂ S ₅ = 75: 25 in terms of molars, crushed using a mortar, and mixed. Next, a solid electrolyte in a glass state was obtained by performing a milling treatment for 10 hours with a planetary ball mill. Then, the obtained glass-state solid electrolyte was annealed in an inert gas atmosphere to obtain a glass-ceramic state solid electrolyte. The annealing treatment temperature was determined with reference to the temperature of the crystallization peak obtained by differential thermal analysis measurement.

The ionic conductivity of the obtained solid electrolyte was measured by the AC impedance method and found to be 7.0 × 10 ^-4 S / cm.

(Example 1)
_{LiNi 0.8} Co _0.15 Al _0.05 O ₂ (average particle size: 5 μm) and the solid electrolyte 75Li ₂ S-25P ₂ S ₅ in the glass ceramic state were prepared as positive electrode active materials and mixed in a mortar. .. The obtained powder was formed into a film on a copper foil in which a binder and a conductive auxiliary agent were uniformly arranged, and pressed to prepare a positive electrode layer of Example 1.

In Example 1, the positive electrode layer was produced by the production method (2) described in the section “F-2. Method for producing the positive electrode layer”. In this case, since no organic solvent is used, the concentration of the organic solvent contained in the positive electrode layer is 0 ppm.

(Comparative Example 1)
The positive electrode layer of Comparative Example 1 was prepared by the same method as in Example 1 except that the binder and the conductive auxiliary agent were not arranged on the copper foil.

(Example 2)
Graphite and the solid electrolyte 75Li ₂ S-25P ₂ S ₅ in the glass-ceramic state were prepared and mixed as the negative electrode active material. The obtained powder was formed into a film on a copper foil in which a binder and a conductive auxiliary agent were uniformly arranged, and pressed to prepare a negative electrode layer of Example 2.

In Example 2, the negative electrode layer was produced by a manufacturing method that does not use an organic solvent, as in Example 1. In this case, since no organic solvent is used, the concentration of the organic solvent contained in the negative electrode layer is 0 ppm.

(Comparative Example 2)
The negative electrode of Comparative Example 2 was produced by the same method as in Example 2 except that the binder and the conductive auxiliary agent were not arranged on the copper foil.

(Manufacturing of all-solid-state battery)
Using each of the layers (positive electrode layer and negative electrode layer) obtained in Examples 1 and 2 and Comparative Examples 1 and 2, an all-solid-state battery including a positive electrode layer, a solid electrolyte layer, and a negative electrode layer was produced.

(Adhesion evaluation)
In the all-solid-state battery using the positive electrode layer and the negative electrode layer produced in Examples 1 and 2 and Comparative Examples 1 and 2, the adhesion between the positive electrode mixture layer and the negative electrode mixture layer and each current collector was evaluated. .. The adhesion was evaluated by winding an all-solid-state battery around a round rod having a diameter of 10 mm and visually observing the degree of cracks generated between the positive electrode mixture layer and the negative electrode mixture layer and each current collector. The results are shown in Table 1. Those with no cracks and showing strong adhesion are marked with "○", those with partial cracks and intermediate adhesion are marked with "△", and those with cracks throughout and showing weak adhesion are marked with "○". It is indicated by "x".

As shown in Table 1, both Examples 1 and 2 had high adhesion strength. It is considered that this is because the binder arranged near the current collector enhances the adhesion strength. On the other hand, in Comparative Examples 1 and 2, since the binder was not arranged near the current collector, the adhesion strength between the current collector and the mixture layer was low.

(Electronic conductivity measurement)
The electron conductivity was measured in an all-solid-state battery using the positive electrode layer obtained in Example 1 and Comparative Example 1 and the negative electrode layer obtained in Example 2 and Comparative Example 2. The results are shown in Table 2.

As shown in Table 2, there was no significant change between Example 1 and Comparative Example 1. This is because, in Example 1, the binder concentration in the vicinity of the current collector is high, and the binder inhibits the electron conductivity. However, in order to ensure the electron conductivity, the concentration of the conductive auxiliary agent is high in the vicinity of the current collector. Is considered to be. Similarly, when Example 2 and Comparative Example 2 were compared, there was no significant change. This is because, in Example 2, the binder concentration in the vicinity of the current collector is high, and the binder inhibits the electron conductivity. However, in order to ensure the electron conductivity, the concentration of the conductive auxiliary agent is high in the vicinity of the current collector. Is considered to be.

From the adhesion evaluation and the electron conductivity evaluation, it was found that in Examples 1 and 2, an all-solid-state battery having both high adhesion and excellent battery characteristics can be obtained.

As described above, in the all-solid-state battery 100 according to the present embodiment, the positive electrode mixture layer 21 containing at least the positive electrode active material 2 and the binder 4 formed on the positive electrode current collector 6 and the positive electrode current collector 6 is formed. A negative electrode layer 30 including a positive electrode layer 20 including the above, a negative electrode current collector 7, and a negative electrode mixture layer 31 formed on the negative electrode current collector 7 containing at least the negative electrode active material 3 and the binder 4, and a positive electrode. An all-solid battery 100 comprising a solid electrolyte layer 40 containing at least an ionic conductive solid electrolyte 1 arranged between the mixture layer 21 and the negative electrode mixture layer 31, wherein the positive electrode mixture layer 21 is provided. The concentration of the solvent contained in at least one layer selected from the group consisting of the negative electrode mixture layer 31 and the solid electrolyte layer 40 is 50 ppm or less, and at least one layer selected from the positive electrode mixture layer 21 and the negative electrode mixture layer 31. The concentration of the binder 4 contained in is higher in the vicinity of the positive electrode current collector 6 or the negative electrode current collector 7 than in the vicinity of the solid electrolyte layer 40.

In the all-solid-state battery 100 according to the present embodiment, the concentration of the solvent (organic solvent) contained in at least one layer selected from the group consisting of the positive electrode mixture layer 21, the negative electrode mixture layer 31, and the solid electrolyte layer 40 is 50 ppm. The environmental load is small because it is substantially free of solvents. Further, in the all-solid-state battery 100 according to the present embodiment, the concentration of the binder 4 contained in at least one layer selected from the positive electrode mixture layer 21 and the negative electrode mixture layer 31 is higher than that in the vicinity of the solid electrolyte layer 40. Since the value is higher in the vicinity of the body 6 or the negative electrode current collector 7 and the binder 4 has a predetermined concentration gradient in the thickness direction of the all-solid-state battery 100, high adhesion strength and excellent battery characteristics (for example, charge / discharge characteristics) can be obtained. It can be compatible.

Further, in the all-solid-state battery 100 according to the present embodiment, the conductive auxiliary agent 5 may be contained in the positive electrode mixture layer 21. As a result, the electron conductivity in the positive electrode mixture layer 21 can be increased, so that the electron conduction path in the positive electrode mixture layer 21 can be secured.

In the all-solid-state battery 100 according to the present embodiment, the concentration of the conductive auxiliary agent 5 contained in the positive electrode mixture layer 21 may be higher in the vicinity of the positive electrode current collector 6 than in the vicinity of the solid electrolyte layer 40. By having a concentration gradient such that the content of the conductive auxiliary agent 5 increases in the vicinity of the positive electrode current collector 6, the internal resistance of the positive electrode mixture layer 21 in the vicinity of the positive electrode current collector 6 can be reduced. can. Thereby, the output characteristics of the all-solid-state battery 100 can be improved.

Further, in the all-solid-state battery 100 according to the present embodiment, the conductive auxiliary agent 5 may be contained in the negative electrode mixture layer 31. As a result, the electron conductivity in the negative electrode mixture layer 31 can be increased, so that the electron conduction path in the negative electrode mixture layer 31 can be secured.

Further, in the all-solid-state battery 100 according to the present embodiment, the concentration of the conductive auxiliary agent 5 contained in the negative electrode mixture layer 31 may be higher in the vicinity of the negative electrode current collector 7 than in the vicinity of the solid electrolyte layer 40. .. By having a concentration gradient such that the content of the conductive auxiliary agent 5 increases in the vicinity of the negative electrode current collector 7, the internal resistance of the negative electrode mixture layer 31 in the vicinity of the negative electrode current collector 7 can be reduced. can. Thereby, the output characteristics of the all-solid-state battery 100 can be improved.

The all-solid-state battery according to the present disclosure has been described above based on the embodiments and examples, but the present disclosure is not limited to these embodiments and examples. As long as the gist of the present disclosure is not deviated, various modifications that can be conceived by those skilled in the art are applied to the embodiments and examples, and other embodiments constructed by combining some components in the embodiments and examples are also available. , Included in the scope of the present invention.

The positive electrode layer, the negative electrode layer, the solid electrolyte layer, and the all-solid-state battery using the positive electrode layer, the negative electrode layer, and the all-solid-state battery using the same are expected to be applied to a power source for portable electronic devices and an in-vehicle battery.

1 Solid electrolyte 2 Positive electrode active material 3 Negative electrode active material 4 Binder 5 Conductive aid 6 Positive electrode current collector 7 Negative electrode current collector 20 Positive electrode layer 21 Positive electrode mixture layer 30 Negative electrode layer 31 Negative electrode mixture layer 40 Solid electrolyte layer 100 All solid battery

Claims (5)

A positive electrode layer including a positive electrode current collector and a positive electrode mixture layer containing at least a positive electrode active material and a binder formed on the positive electrode current collector, a negative electrode current collector, and a negative electrode current collector are formed on the negative electrode current collector. A solid electrolyte having at least ionic conductivity, which is arranged between the positive electrode mixture layer and the negative electrode mixture layer, and the negative electrode layer having at least the negative electrode mixture layer containing the negative electrode active material and the binder. An all-solid-state battery comprising a solid electrolyte layer comprising.
The concentration of the solvent contained in at least one layer selected from the group consisting of the positive electrode mixture layer, the negative electrode mixture layer, and the solid electrolyte layer is 50 ppm or less.
The concentration of the binder of the positive electrode current collector vicinity of the positive electrode mixture layer is not less than 10 times the concentration of the binder of the solid electrolyte layer adjacent the positive electrode mixture layer,
The negative electrode wherein the adhesive layer density of the negative electrode current collector near the binder is the least 10 times the concentration of the solid electrolyte layer and the binder in the vicinity of the negative electrode mixture layer, all-solid-state battery. The all-solid-state battery according to claim 1, wherein the positive electrode mixture layer contains a conductive auxiliary agent. The all-solid-state battery according to claim 2, wherein the concentration of the conductive auxiliary agent contained in the positive electrode mixture layer is higher in the vicinity of the positive electrode current collector than in the vicinity of the solid electrolyte layer. The all-solid-state battery according to claim 1, wherein the negative electrode mixture layer contains a conductive auxiliary agent. The all-solid-state battery according to claim 4, wherein the concentration of the conductive auxiliary agent contained in the negative electrode mixture layer is higher in the vicinity of the negative electrode current collector than in the vicinity of the solid electrolyte layer.

Images